Height Gain and Naismiths rule

this map section shows many contour lines

below shows the area covered by the small map section above

this picture was taken on the ridge just south of Coire Odhar looking North towards Cairn Toul

a contour is
more than just a brown line

when you look at a map you will see many brown lines

these are contour lines

they are "imaginary lines"
in as much as they do not signify actual linear features (like a blue line
signifies a river)

however they are one of the most important and therefore useful items of information that can be gained by looking at a map.

with practice these lines can tell you an awful lot

establish which way up
the land is that the
contours represent

if you come across a hill that you misread as going down rather than up,
this is usually because you misread the contour lines

we must start by looking at exactly what a contour line is.

it is a line of connecting ground that is all the same height above sea level.

it's shape is influenced by the shape of the ground it represents

an example of a map section
totally dominated by contours

Image produced from multimap.com

with experience you can look at a map section and gain left it shows many contour lines
the following information can quickly be attained

the main summit has steep contour lines on all sides therefore it is a steep sided mountain

the slope at the top left and the one at the top right are the only even slopes as the contours are evenly spaced

The CIC hut is at the top of a valley dropping down to the North

I could "go on" but learn how to interpret contour information for yourself

coming soon on a new page

land shapes and how contours represent these shapes
showing both pictures and the contour line diagrams
representing land forms such as
summit, valley, ridge, knoll, arete, etc.

please re-visit soon

vertical interval

vertical interval is the amount of height between the contour lines, in most cases this is ten meters,

but in some flatter areas it is 5 meters

on some larger scale maps it is different again, so always check the vertical interval between contors

the vertical interval on the map section of Ben Nevis above is 15 meters

index contours

all contours re usually drawn in brown

but every so often a contour line is drawn as a thicker brown line this is the "index" contour

an index contour is drawn every 50 meters to allow easier adding of contour numbers, an help with the visualisation of the land shape

the index contours on the map section of Ben Nevis above are every 75 meters

work out how much time to add to your route
to allow for contours

to ensure you allow enough time for your walk
you need to know how much time must be allowed for contour lines

in effect you need to know the amount of height gain, and to a lesser extent height loss

once this is know (along with the route distance) this time is added together using a formula known as Naismiths rule

if you are unsure about Naismith's rule, see my web page navigation distance

but a simple formula for height gain is :

a simple calculation of height gain using contours is to :

count the contour lines that you cross going up hill i.e. height gain

then add 1 minute per contour line

after checking the vertical interval is 10 meters (check this for the map you are using)

if your vertical interval is different to 10 meters then adjust your time as you roughly average 10 meters per minute of ascent

some people a also add time for descent (although this is a matter of personal choice) the formula often used is 1 minute for each 20 metres of descent